Railway signal system



May 7, 1935.

L. ESPENSCHIED RAILWAY SIGN-AL SYSTEM Filed Aug. 241, 1926 3Sheets-Sheet l INVENTOR zzovo 3BPEIV6CH/ED ATTORNEY 1935. L. ESPENSCHIED2,000,166

RAILWAY SIGNAL SYSTEM Filed Aug. 24, 1926 3 Sheets-Sheet 2 /2 H I lINVENTOR Z; 0 ya ESPf/VS 6/1/50 mrw ATTORNEY May 1935. ESPENSCHIED2,000,166

RAILWAY S IGNAL SYSTEM Filed Aug. 2 1926' 3 Sheets Sheet 3 INVENTOR 14m0 zis f/vscflmo ATTORNEY Patented May 7, 1935 UNITED STATES v r l, 1 0

' RAILWAY SIGNAL SYSTEM i. Lloyd Espenschied, Hollis, N. Y. 7Application August 24, 1926, SerialNo. 1211,14; '1 Claims; (01. 246-L63)This invention relates to railway signal and automatic traincontrolisystems, and more particularly to the means employed fortransmitting the signal indications between the wayside I and the train.

.In abroad sense, the present invention em-' sidecircuit, (2) thetransmission of the power.

backagain to the train after having been controlled in accordance withtraific conditions ahead and 3) the actuation of the signal device onthe train by the return transmission. The earlier embodiment providedmeans for discriminating between the outgoing and the returntransmission and of thereby insuring that the energy which is effectivein operating the signal device is that which has been subjected towayside control in accordance with traflic conditions.

The system of the present invention from that .disclosed in the earlierpatent in sev-' eral respects but particularly in the method employed'for discriminating between the exciting energy sent into the waysidesystem and the signaling energy returned to the train. In accordancewith the present invention two wayside circuits are set up, one for theoutgoing .and' the other for the return transmission and are sosuperimposed one upon. the other, as to enable the same waysideinductors to be employed for both circuits. Discrimination between thesetwo circuits is accomplished by disposing them in a mutually balancedmanner. V r

The invention includes the application .of these features to bothcontinuous and discontinuous control systems. In the continuous controltype of system, the. wayside inductors which receive the energy from andreturn it'to the train, extend along the wayside moreor less coincidentwith the block sections' The track rails themselves are preferablyutilized asthe wayside inductors. In the discontinuous control type ofsystem the wayside inductor elements are localized coils. An object ofthe invention will therefore be appreciated tobethat of providing aninductive type of system employing an inert wayside circuit and onecapable of being employed for either intermittent or continuous traincontrol. Further objects, such as those of obtaining more than'twosignal indiffers. nated iron core and is so mountedonthe train dicationsand o providing a system which opera ates in accordance with the closedcircuit principle, will be evident from the illustrative em I bod-imentsshown in the accompanying drawin'gsinwhichz- Figures :1 and 2 show. theapplication of invention in an intermittent} control type of system,Figure l being the trainecarried portion, and Figure 2 aschematicshowing of the wayside portion; of the system. i Q a Figure 3shows the application of my invention to a continuous control type ofsystem; the wayside system being shown in asimplifled Figure 4 shows awayside system' similar to that shown: in Figure 3, superimposed uponor- 15 dinary block signal" track circuits.

Referring to-Figure 1, alternating-current energy is generated aboardthe train by gene a or I, The energy is passed through transformer 2,through conductors 3,1, and 5, 6 to-the train 20 inductor coils I and 8.These coils may b tuned individually to the frequency of the generatorby means of. condensers 9 and I0. Each-of the coils l and 8 embracesja-ninverted U-shaped lamias to pass over and coaet inductively withcomplementary coils disposed in the wayside' The wayside'coils,designated H and 12, in Figurel2, are likewise provided with U-shapedlaminated ironcores. The wayside cores are made 3;) of large. sizebecause they are intended in themselves, without their coils, to afiectthe traincarried circuit, as will be described. When the train passesthewayside control point, train 'coil 1 links magnetically withwayside-coil H and train-0011 8 with wayside coil 12,. The wayside-coilsmaybe tuned individuallyby densers l3 and M. The wayside coils are con--neeted together in the manner indicated and their'circuit is extended bymeans of conductors 41) I5, 16' thrQ gh the contacts of relays 11,18 totransformer l9.- I v 1 The two train coils and the two wayside coils areso connected in their respective circuits current from generator Iflowing through co'iis l and .8 induces current'in coils .H .and J2which are connected in series aiding relation with re. spect to eachother in circuit 15, L6, This current flows through conductors l5 andIGJ'and' through the primary winding (1 (which is icen- 5.0 ter-tapped)of transformer [9.1 The current so established induces an E. M. F, inthe secondary winding of transformer 49. Said winding 1) sends currentthrough a c:ircuityvjiriich' may be traced as :follows, the relativepolarity PATENT "ow s being that which obtains at some one instant:Conductor 20 to the center tap'of the primary a of transformer l9,through the two halves of the transformer winding in mutually parallelopposing relation, thence in parallel along conductors !5 and I6,through coils H and i2, mutually in parallel, and back on conductor 2|to secondarywinding b.

Thus the wayside circuit receives an excitation in'one sense, asthroughthe two coils H, l2

. connected in series and poled to be aiding around the circuit l5, I6,and transmits current back in another sense through the two sides, !5[

and I6, of the circuit in parallel connected by a third conductor 2|.

train. The return-transmission wayside circuit,

(traced by 26, i5 and |6.i n parallel, H and [2 in parallel, 2i andsecondary b), is therefore bal ahead and non -interfering with respectto the l mutually aiding with respect to and cause current to flow in acircuit superposed upon and balanced with'respect to circuit 5, 6, theflow being at some one instant as'follows: Along conductors 5, 6 :inparallel; 3;4 in parallel to the secondary of the current supplytransform er 2; through the two'halves ofthis'winding in parallelopposing relationto the center tap and thence along conductor 22;throughwinding 23' of the receiving relay 23,'and back on conductor 24 to thepoint midway betweencoils 1 and 8., By passing the received currentthrough the train inductor coils in this balanced'rna'nner, it isimpressed upon the actuating winding of the receiving relay to theexclusionof the outgoing current; be of the A. C. excited type, currentfrom the generator being supplied to the magnetizing windings throughconductors. 25, 26.

With respect to the use of the two pairs of inductors simultaneouslyforthe establishment of two distinct transmission paths, one fortransmittingthe exciting current to the wayside signal location and theother for selectively transmitting the signal indicating currents backtothe train} the-following further elucidation may be useful: Thetrain-carried inductors 1, ,8 operate'in'series in circuit 5, 6 todeliver power to wayside inductors 1!,12. The latter in turn operatein'series to transmit the'power over oncuit I5, Hi, to the primary a oftransformer IS. The return'transmission path may be regarded asoriginating in secondary winding 1), and extends along 26, along {5, [6'taken in parallel,

through wayside inductors ll, 12 taken in parallel, along 2! back to thesecondary 12.. Thus the wayside inductors operate in parallel for thereturn transmission to induce currents in train inductors land '8 whichfiowcorrespondingly in parallel along conductors 5, 6, along 3, 4,traverse conductor 22; relay winding 23 and thence over conductor llba'ck to the inductors. Thus the The wayside inductor coils' are thusenergized in a mutually paralle1 and opposite sense for retransmissionback to the e The receiving relay is illustrated to tively transmit backto the train the energy carrying the signal indications. The way inwhich the signal indications are actually impressed uponand taken fromthe return transmission path will now be described. The'basis ofsignaling which is preferred for this discontinuous type of system isone wherein the wayside control elements are made to tend normally togive a stop indication, and wherein the giving of a'caution or a clearindication is accomplished by overcoming the' stop" indicationandsubstituting for it'the safer indication. Accordingly, there is providedin the present invention a tripping means which gives a stopindicatimrunless positively displaced by a caution or clear indication.The tripping means comprises a balanced circuit centered about the3-winding balancing transformer, illustrated as included within thedotted rectangle 39. The B-Winding balancing transform er is of the typecommonly known in telephone engineering as ahybrid 'coil and need not bedescribed in detail. The circuit includes on one side of the balanceboth of the train coils I and 8 taken in series and aiding in theireffects and on the other side a balancing coil or coils 21, 28. In caseswherecondensers 9, 10 are employed balancing condenser 29 is included onthe balancing side. -The inductance of ,coils 27--2S is made equal tothe combined series connected inductance of coils land 8 when over thecores of wayside coils l I. and 13, with the circuit E5-I6 open. e

Under this condition the circuit is balanced so that no current isinduced in the middle winding of thehybrid coil, the electromotiveforces induced in this winding from the two halves of'the primarywinding being equal and pr posed. When the j circuit is unbalanced theseforces are unequal and a' resultant current flows in a relay 3!connected in circuit with the middle winding of the hybrid coil.

With the wayside circuit open, as is the case for the stop condition,the circuit for including current in the circuit of relay 3! tends tobecome balanced as'the train coils pass over the wayside inductor cores.As a result, the currentin relay 31 is greatly reduced and the relaycontacts open. The train signal circuits are arranged so that this givesa stop indication. A stopindication will then also be given in case offailure ofrthe source of current When the trainis between control pointsthe circuit is unbalancedand relay 3! is held closed byourrent'transmitted from the generator I through the balancingtransformer rectangle 3Q.

Thus it will be seen that one indication, the stop indication, is passedto the train merely by the action of the cores of Wayside coils II andE2 in unbalancing atrain-carried circuit. In' ;actual operation thisaction comes into play upon'the opening of circuit l -l6 by the re-'indicated by the lease :of relayfl; Relays l1 and 18 will be understoodto be operated from. the track circuit of the usual type of block signalsystem.

The safety indication is given when the wayside circuit is in thecondition illustrated in Figure 2. The circuit .is'so arranged that whenthe train passes over the wayside control point therelativeinstantaneous polarity of the energy transmitted back to the; train,.anth which enters winding 23 of the receiving relay, will be such "asto move. the armature of the receiving relay-to, say, the left contact.This causes the. actuation of relay-32 which 'in'turn is made todisplaya clear indication 'throughthe' ap-,.

propriate local circuit arrangements. These ar-Q energized and functionsto give-the. caution signal. It will be understood that the signalindications described above may be employed in conjunction with wellknown'types. of-speed control devices to control automatically the speedof the train.

The wayside signaling relaycontacts are illustrated connected in thewayside circuit ate. point which is common to both of the twosuperimposed transmission circuits, one receiving from the train and theother transmitting to the, train. They could as well be placed in thecircuit at 20, 21, where theywould be confined to the path transmittingto the train, and the transformer l9 would receive power from the trainirrespective of the wayside relays. I a

It is desirable to note also that wayside transg former. I9, constitutesa means for terminating the power-supply transmission channel and forturning it back upon itself over a superimposed balanced channeltransmitting back to the train. By thus acting to interconnect twochannels which otherwise are balanced one against the other, thetransformer is really a means for effecting a total unbalance betweenthe two chan nels in question, and in turn an unbalance between thetransmitting and the receiving circuits upon the train. The unbalancingaction is thrown in or out by relay l1, and the relative sense orpolarity of the unbalance is controlled by relay I8.

This constitutes. another way of looking upon the modus operandi of thepresent type of system, including the continuous as well as theintermittent control system.

Referring now' to the continuous control sys-' tem of Figure 3;alternating-current energy from generator I is transmitted throughtransformer 2, along conductors 3, 4 and 5, 6 to the traincarriedinductors l, 8. These coils are disposed on the train in proximity tothe track rails H,

J H for the purpose of inducing current therein.

current flows longitudinally along the rails to the end of the blocksection, and returnsover a third conductor 2| provided along"theright-ofway, as by being carried on the'wayside pole line. Thetransmission path may be traced gas follows: along rails ll, I 2 inparallelpalongcone ductors, I 5, l6 in parallel; through the two halvesof the'winding of transformer l9v non-induc-v tively, to the center tap;along conductor 2|; I

through ia ,-path which includesathe wayside: relaycontacts and thewinding ofwtransformer 19,;(which becomes the primary winding); backalong the conductor 2| to the other end ofthe block; non-inductivelythrough the centertapped coil I 9; and thence back tothe two rails- Thiscircuit constitutes a. closed circuit ,loop

which'receives energy inductively from the ingtrain. I

"The energy thus trolled in accordance with signalindications in amanner to be described subsequently; is ,re. transmitted to the train inthe following man: ner;-current flowing in the loop circuit justdescribed induces an E. M. F. in the secondary (center tap'ped) windingof transformer -18. This causes current to flow transversely between thetrack rails over a path which startsincone ductors 5,16 and includes therails 1 I, I2 and is completed through the wheels and axles of areturn-transmitting circuit as wellas a non: interfering energy pick-upcircuit. yInjth-e form described the two rails in parallel form thewayside energy pick-up circuit while vin series they function asthereturn-transmitting circuit. .It will be understood that conditionscould bereversed, i. e., the usual transverse. rail circuit could beutilized for transferring the energy to.

as to be mutually aiding with respect to circuit 22, 24 and to sendcurrent into winding-23'-.of

received, after being .the train. In this way the trackrails serve asthe receiving relay. An amplifier A, preferably J of. the vacuum-tubetype, may be inserted in the circuit 22, 24 to increase the poweravailable for operating the receiving relay. The circuit of 9'. Thereceiving relay is preferably of their-1+ duction type, supplied withexciting current from the generator l over conductors 25,26.

the pick-up coils may be tuned by a condenser Q 7 The system thus fardescribed constitutes-fan electric wave transmission path which, extendsfrom the train to the waysidepoint ofsignal control and then back againto the train. Both the outgoing and the return .paths are metalliccircuits, and the looped transmission path, so

formed is to be distinguished'from a circuit com:

' posed of a single wire looped out and back. This looped path isestablishedcontinuouslyduring the occupancy of a block by the train, andthe return transmission is continuously available for the transmittingof signaliindications to the train. The signal indicationsarertransmitted as follows: I 1

1. In accordance with the closed 'circuit prim ciple of operation, thenormal return transmission accomplishes by its receipt on the train theclear or proceed indication. The train relay is assumed to be throw'n'tothe left, as showrr'for this condition,

2. For'the transmitting of the caution? indication'relay I8, is assumedtobe' released by the wayside block Isignal systenr effect of this is toreverse the relative instantaneous Q polarity of the current supplied tothe rails from opens. the local train circuits, resulting in the displayof the'danger indication in the locomotive cab and in the application of"a stringent speed limitation or a stop in accordance with practice well'known in the art.

The wayside transmissionpaths of Figure 3 I may be superimposed upon theordinary-block signal track circuits, as illustrated in Figure 4. Thetrack'circuits are here. assumed to be of the direct-current-type. Thesuperposition principle wouldbe the same, however, were theyot thealternating-current type. In the latter case the alternating-currentprovided on the train would bechosen to'be sufiiciently different infrequency from the alternating-current of the blocksystern to permit ofseparating the two sets of currents by frequency-selecting:means.

Referring now to Figure gfthe several block sections are designated I,-2, -3, 4.

The direct current for" block -2, for example, issupplied by battery-B2.Ihe current flows through the foli lowing path: the contacts of relayR1, through one set or" windings of transformer T2, to the rails AA; andalong the rails to relay R2. The track relays are of the polarized type,having two sets of contacts, thosedesignated by the letter N-being thecontacts controlled by the neutral winding-and those designated by the'letter P being 'the contacts which are controlled by a change in thepolarity of the-current. When the current is interrupted; the N'contactarms 7 release but the P contact arms hold. When the current isreversed-the N contact arms hold but the- P contact arms reverse. e'lhus, the regular block-signal direct-current circuit portion of Figure4 will be understood to operate as follows: A train-occupying block 1causes the N2 contact arms of-relay R1 to release. This reverses batteryB2 of block 2 which in tur'n'reverses the P3 contact arms of relay R2.Battery I B3 is applied to block 3 in a normal manner andas'a resultrelay R3 holds both sets of contact arms Ni and P4 in the normal clearcondition. These operationsare illustrative ofthe ordinary block signalandare not novel. "The portion of the wayside'system which is new and 'apart of the present invention, as

described in connection with'Figure 3, is shown as superimposed uponthe. ordinary block circuit and may be traced in block 2 of Figure 4 as,

7 follows: 'The energ y supply circuit is, from the train intorails AAin'parallel, through the two line windings of transformerv T2 in"parallel mu-v tually opposing 'relation, along two of the N2 contactarms inparallel, to B2. Were the N2 contact arms drawn up by theactuation of relay R1, the circuit would continue: through one contactarm of P2, through the winding .(actu ally. the primary winding), oftransformer T2,

, back through "the other. contact arm of Pz and 75.

back to the other end of the block over conductrain upon the rails.

When currentv is induced by a passing train in the longitudinalwayside'pick-up circuit AA, K, the current tends to be passed back tothe train over a transverse circuit, formed of the railsin series; asfollows: .The two secondary coils of transformer. T2 have series aidingE;-,M. FLs induced in them as the result of current'flow 'intheprimarycircuit just delineated. The secondary E. M. Ffs tend to set up currentflow around a circuit J5, it which is closed upon itself at one end bythe. contacts of N2 and battery circuit B2, which includes the two railsAA in'series in the circuit, andwhich at the rail end is closed by theshort-circuiting' effect of the The: ordinary D. C. track circuits ofFigure 4 illustrate the three signal indications, stop, caution, andcleaiyto be set up for blocks 2, 3 and 4 respectively. 'In block 2 thestop indication is passed to the train-simply by opening at N:

the circuit which-picks up the energy from the train: Thetrain=generated energy is not returnedto the train and, therefore, thereceiving relay on the train'is released. In block 3 the caution signalis transferred to, the train by virtue of the relative reversal at P3 ofthe current which is fed back to the train. This results in a reversalof the train-carried relay in the mannerpreviously explained. In block 4the clear or proceed signal condition is transferred to the trainbecause the circuit is in suchconditidn as to send energy back to thetrain in relatively normal phase relation. Thus a train in passing alongfrom block 4'to 3 to 2 will meet successively, and be subjected to control in accordance with, the clear, caution and stop indications.

Referring to the train-carried arrangement disclosed in Figure 3 it willbe noted that a separate set of sending'and receiving coils is employed.Actually one pair of coils could be used as is done in the arrangementof Figure l. The separate coil arrangement has the advan- 'tage ofimproving the balance separation obtained between the superposedlongitudinal and transverse circuits. In other words, the train re--ceiving circuit is subject to less direct influence fromthe transmittingcircuit because of the transmission loss which intervenes between thesending and receiving coils by virtue of their separation and by' virtueof their being placed on opposite sides (front and rear) of one ormoretrucks of the locomotive.

Having now describedthe invention, what I claim .is:'

1. Awayside circuit for train'control purposes comprising two inductors,means for connecting the two inductors in parallel with each other intheciicuitfor transmission in one direction, from or to the train, andin serieswith each other in the circuit for transmission in the .reversedirection, means in the Wayside for interconnecting the two superimposedpaths thus formed, together with means on the train whereby energy isreceived from said wayside circuit to thesubstantial exclusion of theenergy which is transmitted into it.

2. In a train control system, a train-carried alternating currentsupply, a train-carried inductor unit including a combination oftransmitting and receiving inductor coils, said coils being capable ofbeing balanced in respect to the direct efiect of said source, togetherwith an inert wayside circuit provided with a pair of inductors forreceiving power from the traincarried source and for selectivelyinfluencing the train-carried receiver in accordance with trafiicconditions ahead. i

3. In a train-control system, a train-carried inductor Winding with acoacting wayside inductor forming one inductive coupling, a secondtrain-carried inductor winding with a coacting wayside inductor forminga second inductive coupling, a connecting circuit on the train whichcombines theinductive effects of said two train-carried windings inseries witheach other in the circuit for the transmission of signaling,

source of alternating current, a pair of traincarried inductor coilssupplied with alternating current from said circuit, a train-carriedsignal receiving circuit utilizing the same pair of inductor coils, andmeans for so connecting the receiving circuit and saidfsource to theinductor coils as to prevent the alternating supply current fromdirectly affecting the receiving circuit; together with a waysidecircuit comprising two inductors and means for, connecting them inparallel with each other in the circuit for transmission of signalingcurrent in one direction, from or to the train, and for connecting themin series with each other in the circuit for transmission in the reversedirection.

5. In a' system for transmitting signals between a train and thewayside; a two-wire circuit for transmitting in one direction betweenthe vehicle and wayside, a circuit derived in part therefrom fortransmitting in the reverse direction, comprising a third Wire connectedto the midpoint of the two-wire circuit at each end and completed by theconductors of the two-wire circuit working in parallel, a transformer inthe wayside, including primary and secondary windings, and'means in onewinding thereof to make said midpoint connection, oneof said windingsbeing included in said two-wire circuit and the other being included inthe third wire of the derived circuit. i

6. In a train signaling system, the trackside arrangement which includesa two-wire circuit for transmitting signal current in one directionbetween train and trackside, a circuit derived in part therefrom fortransmitting signal current in the reverse direction comprising a thirdwire connected at each end to a midpoint of the twowire circuit andcompleted by theconductors of the two-wire circuit working in parallel,said circuits including a transformer having primary and secondaryinductive elements, one of said eIementsbeing divided into two equalcoils which rent from directly affecting the receiving circuit;

together with a wayside circuit comprising two inductors and meansincluding a transformer for connecting them in parallel with each other.in the circuit for transmission of signaling current in one direction,from or to the train, and

for connecting them in series with each other in the circuit fortransmission inthe reverse direction.

I LLOYD ESPENSCHIED.

